During the summer of 1845, a "blight of unusual character" devastated Ireland's potato crop, the basic staple in the Irish diet. A few days after potatoes were dug from the ground, they began to turn into a slimy, decaying, blackish "mass of rottenness." Expert panels convened to investigate the blight's cause suggested that it was a result of "static electricity" or the smoke that billowed from railroad locomotives or "mortiferous vapours" rising from underground volcanoes. In fact, the cause was a fungus that had traveled from America to Ireland.

"Famine fever"--dysentery, typhus, and infestations of lice--soon spread through the Irish countryside. Observers reported seeing children crying with pain and looking "like skeletons, their features sharpened with hunger and their limbs wasted, so that there was little left but bones, their hands and arms." Masses of bodies were buried without coffins, a few inches below the soil.

Over the next ten years, 750,000 Irish died and another 2 million left their homeland for Great Britain, Canada, and the United States. Freighters, which carried American and Canadian timber to Europe, offered fares as low as $17 to $20 between Liverpool and Boston--fares subsidized by English landlords eager to be rid of the starving peasants. As many as 10 percent of the emigrants perished while still at sea. In 1847, 40,000 (or 20 percent) of those who set out from Ireland died along the way. "If crosses and tombs could be erected on water," wrote the U.S. commissioner for emigration, "the whole route of the emigrant vessels from Europe to America would long since have assumed the appearance of a crowded cemetery."

At the beginning of the 19th century, only about 5,000 immigrants arrived in the United States each year. During the 1830s, however, immigration climbed sharply as 600,000 immigrants poured into the country. This figure jumped to 1.7 million in the 1840s, when harvests all across Europe failed, and reached 2.6 million in the 1850s. Most of these immigrants came from Germany, Ireland, and Scandinavia, pushed from their homelands by famine, eviction from farm lands by landlords, political unrest, and the destruction of traditional handicrafts by factory enterprises. Attracted to the United States by the prospects of economic opportunity and political and religious freedom, many dispossessed Europeans braved the voyage across the Atlantic.

Each immigrant group migrated for its own distinct reasons and adapted to American society in its own unique ways. Poverty forced most Irish immigrants to settle in their port of origin. By the 1850s, the Irish comprised half the population of New York and Boston. Young, unmarried, Catholic, and largely of peasant background, the immigrants faced the difficult task of adapting to an urban and a predominantly Protestant environment. Confronting intense discrimination in employment, most Irish men found work as manual laborers, while Irish women took jobs mainly in domestic service. Discrimination had an important consequence: it encouraged Irish immigrants to become actively involved in politics. With a strong sense of ethnic identity, high rates of literacy, and impressive organization talents, Irish politicians played an important role in the development of modern American urban politics.

Unlike Irish immigrants, who settled primarily in northeastern cities and became active in politics, German immigrants tended to move to farms or frontier towns in the Midwest and were less active politically. While some Germans fled to the United States to escape political persecution following the revolutions of 1830 and 1848, most migrated for quite a different reason: to sustain traditional ways of life. The industrial revolution severely disrupted traditional patterns of life for German farmers, shopkeepers, and practitioners of traditional crafts (like baking, brewing, and carpentering). In the Midwest's farmland and frontier cities, including Cincinnati and St. Louis, they sought to reestablish old German lifeways, setting up German fraternal lodges, coffee circles, and educational and musical societies. German immigrants carried important aspects of German culture with them, which quickly became integral parts of American culture, including the Christmas tree and the practice of Christmas gift giving, the kindergarten, and the gymnasium. Given Germany's strong educational and craft traditions, it is not surprising that German immigrants would be particularly prominent in the fields of engineering, optics, drug manufacture, and metal and tool making, as well as in the labor movement.